DNA Replication Flashcards
Aneuploidy
abnormal amount of chromosomes, can be more or less
What molecule is released when a nucleotide is added to the growing DNA chain
PPi (nucleotides are triphosphates)
DNA replication takes how long
6-12 hours on average
Mitosis takes how long
Always an hour
Prokaryotes have how many origins of replication?
1
Eukaryotes (humans) have how many origins of replication?
30,000 to 50,000
Eukaryotic origin examples
AT rich areas, CpG islands because these kinds of areas are usually open and active due to transcription
Human cells take how long to replicate
8-24 hours
Origin is recognized by what complex?
Origin recognition complex binds to the Origin in late M and early G1
CDC 6 stands for
Cell division cycle 6
CDT 1 stands for
DNA recognition 1
MCM helicase complex stands for
Mini Chromosome Maintenance Helicase complex
Licensing replication means
DNA can only be copied once
The binding of the MCM creates the…
replication fork
What two proteins need to be bound to the ORC to allow replication to proceed?
cdc6 and cdt1
What is the function of cdc6?
Binds to the ORC
What is the function of cdt1
binds to the MCM and brings to the ORC
When does cdc6 peak in the cell?
G1 and S
When does cdt1 peak in the cell
M and G1
What is the role of gemini in DNA replication
Inhibits cdt1
What three enzymes are needed for DNA replication
DNA primase/ Pol Alpha - lays down primer
DNA Pol Delta - copies template
Topoisomerase - prevents supercoiling
What is the role of Replication Protein A
When MCM unwinds the DNA and it becomes ssDNA, to prevent degradation by the cell it is coated by RPA for protection
What is the prokaryotic equivalent of topoisomerase I
DNA Gyrase
What drugs target topoisomerase
Antibiotics - quinolone (cipro, naldixic acid)
Anti tumor - etoposide, doxorubicin
DNA ligase uses what energy molecule to create a phosphodiester bond
ATP
What two things happen at the replication fork?
Separation of the DNA strands and release of the histones
Cohesion is found where and when
immediately before the replication fork and on the newly synthesized strands until separation occurs at anaphase
Why do telomeres cause problems in replication?
Telomeres cause issues in replication because DNA Pol D can only add in the 5’ direction if there is a strand for it to start on. At the 5’ end of the chromosome there is nothing there compared to the 3’ side because the RNA primers can be removed but DNA Pol D cannot add new nucleotides
Telomerase is a
reverse transcriptase
What are 4 possible mechanisms drugs could use to block DNA replication
Block or reduce synthesis of nucleotides
Inhibit DNA Polymerase
Cross link DNA strands so they do not separate
Incorporate nucleoside analog into DNA chains causing weakness and chain termination
How does Acyclovir work
similar to guanosine and i converted to a Acyclovir “nucleotide” and inserted into the chain causing chain termination
How does foscarnet work (Foscavir) and what does it treat
reversibly blocks the pyrophosphate binding site of the viral polymerase stopping the release of PPi and stops the polymerase from continuing. Foscavir treats Herpes
Azidothymidine treats HIV through what action
chain termination (Know more?)
Sustiva treats HIV through what mechanism
Non nucleoside reverse transcriptase inhibitor
Name of clamp that holds DNA Pol Delta to DNA
PCNA - Proliferating cell nuclear antigen
What enzyme complex is responsible for Okazaki fragements
Primase/DNA Pol Alpha
